Search PubMed⌕ Search

Biomedical subjects

P Webster

Publications and source records attributed to P Webster.

123 records · Page 7Linked to original sources
PubMed1986

Endoplasmic reticulum contains a common, abundant calcium-binding glycoprotein, endoplasmin.

The most abundant protein in microsomal membrane preparations from mammalian cells has been identified as a 100 X 10(3) Mr concanavalin A-binding glycoprotein. The glycosyl moiety of the glycoprotein is completely sensitive to endoglycosidase H, suggesting a predominantly endoplasmic reticulum localization in the cell. Using a monospecific antibody it was shown by binding and immunofluorescence studies that the glycoprotein is intracellular. Immunoelectron microscopy showed that the glycoprotein was at least 100 times more concentrated in the endoplasmic reticulum than in any other cellular organelle. It was found to be substantially overexpressed in cells and tissues rich in endoplasmic reticulum. Since it is the major common protein component associated with the endoplasmic reticulum we refer to it as endoplasmin. Calcium-binding studies show that endoplasmin is a major calcium-binding protein in cells, suggesting that at least one of its roles might be in the calcium-storage function of the endoplasmic reticulum. The amino-terminal sequence of endoplasmin is identical to that of a 100 X 10(3) Mr stress-related protein.

Animals↗
PubMed1985

Theileria parva: expression of a sporozoite surface coat antigen.

A monoclonal antibody specific for the Theileria parva sporozoite, which recognizes a determinant on the surface coat and blocks sporozoite infectivity, was used to investigate the presence of the determinant on other stages of the parasite lifecycle. Immunofluorescence techniques did not demonstrate this determinant on the kinete, schizont, merozoite, or piroplasm stages of the parasite. Immunoautoradiography, using a tritiated form of the monoclonal antibody, on sections of infected salivary glands collected from ticks that had fed for 0, 1, 2, 3, or 4 days revealed that the determinant recognized was synthesized predominantly during sporogony, between 2 to 3 days after the tick started feeding. Immunoelectron microscopy was performed on ultrathin frozen sections of infected tick salivary glands incubated with the monoclonal antibody followed by Protein-A--colloidal gold. The antigen or its precursor could be detected in the developing parasite. In ticks fed 2 days, the sporoblast was labeled, both in the cytoplasm and on parasite membranes, often including the nuclear envelope. In sections from ticks fed 4 days, the sporozoite surface membrane was labeled, as were membrane-bounded sporozoite organelles identified as micronemes. Observation by immunofluorescence, on sporozoites incubated with bovine peripheral blood lymphocytes, suggested that the antigen recognized by the monoclonal antibody does not enter the lymphocyte during sporozoite endocytosis. We conclude that synthesis of the antigen or its precursor(s) occurs during sporogony in the feeding tick, at the time of maximal parasite proliferation, and precedes the formation of morphologically mature sporozoites; the antigen's role in the parasite life cycle also appears to be limited to events associated with the sporozoite entry process.

Animals↗
PubMed1985

Identification of a surface antigen on Theileria parva sporozoites by monoclonal antibody.

A mouse monoclonal antibody (mAbD1) that neutralizes sporozoites of different stocks of the protozoan parasite Theileria parva has been used to localize and identify a sporozoite antigen. Protein A-colloidal gold was used to localize bound mAbD1 in immunoelectron microscopic studies. mAbD1 bound to sporozoite antigen, which was evenly spread over the surface of all sporozoites. Immune complexes were obtained by incubation of sporozoite suspensions with mAbD1 followed by Zwittergent 3-14 extraction and precipitation with protein A-Sepharose. One- and two-dimensional NaDodSO4/polyacrylamide gel electrophoretic analyses were performed on these complexes, and a major protein with a molecular size of 68 kDa was identified. Other related components of 52 kDa, 47 kDa, and 28 kDa were also detected. Since antibody to this antigen(s) neutralizes T. parva sporozoites from different stocks, the results could be of relevance to the development of a broad spectrum vaccine against the cattle disease East Coast fever, which is caused by T. parva.

Animals↗
PubMed1985

The entry of sporozoites of Theileria parva into bovine lymphocytes in vitro. Immunoelectron microscopic observations.

In an electron microscopic investigation of the entry of sporozoites of Theileria parva into bovine lymphocytes, the fate of the surface coat of the parasite was traced by immunocytochemical methods. A monoclonal antibody (MAbD1) raised in mice and directed against a surface antigen of sporozoites, was applied to ultrathin frozen sections of bovine lymphocytes infected in vitro. Sites of binding of MAbD1 were localized using a protein A-colloidal gold conjugate as an electron-dense label. The surface of all free sporozoites was labelled. Sporozoites in the process of entering were labelled only on that portion of the membrane not yet tightly bound to the lymphocyte membrane. No label was detected on sporozoites that had completed entry. After fixation with formaldehyde, but not with glutaraldehyde, local areas of labelling were found on lymphocytes in contact with sporozoites and on cells already invaded. The sporozoite organelles, called micronemes, occasionally appeared to contain labelled antigen. No label was found on sporozoites or lymphocytes in control preparations previously exposed to non-specific antibody or treated with protein A-colloidal gold alone. The findings support the conclusion that the sporozoite surface coat, containing the antigen recognized by MAbD1, is shed as the sporozoite enters the host cell.

Animals↗
PubMed1984

The intracellular pathway and assembly of newly formed variable surface glycoprotein of Trypanosoma brucei.

Pulse-chase experiments using L-[35S]methionine suggest that Trypanosoma brucei MITat 1.2 variable surface glycoprotein (VSG) synthesized in the rough endoplasmic reticulum, a process that takes 6-8 min, is shuttled to the Golgi complex 8 min later. Labeling of ultrathin frozen sections with affinity-purified anti-cross-reacting determinant (CRD) IgG followed by protein A-colloidal gold shows that the CRD is localized in the trans-Golgi region. cis-Golgi is not labeled. VSG, when solubilized by treatment with the detergent Nonidet P-40, behaves on sucrose density gradients as a non-membrane protein with a sedimentation value of 5 S. In contrast, VSG solubilized in the presence of Zwittergent TM 3-14 yielded several VSG-containing fractions greater than 5 S, and only the 5S fraction contained the CRD. Lack of the CRD in VSG complexes with sedimentation values greater than 5 S suggests that this determinant is either masked from antibody, perhaps by involvement in polymer formation, or represents the membrane form of VSG recently described by Cardoso de Almeida and Turner [Cardoso de Almeida, M. L. & Turner, M. J. (1983) Nature (London) 302, 349-352].

Animals↗
PubMed1984

Chronic ventilatory failure caused by abnormal respiratory pattern generation during sleep.

A 67-yr-old man presented with a 4-yr history of chronic ventilatory failure in the absence of any restrictive or obstructive ventilatory defect. Detailed neurologic investigations were unremarkable, and the response of minute volume of ventilation to inhaled CO2 was normal. During sleep there was no evidence of upper airway obstruction, and minute volume of ventilation averaged 6.7 L/min, compared with 7.2 L/min during quiet wakefulness. However, sleep was associated with a rapid and shallow pattern of breathing, resulting in high dead space ventilation, inadequate alveolar ventilation, hypoxemia, and hypercapnia. Correction of the abnormal ventilatory pattern during sleep by diaphragmatic pacing abolished all features of chronic respiratory failure. The findings indicate that a disorder of respiratory pattern during sleep can produce chronic ventilatory failure, despite normal respiratory drive.

Aged↗
PubMed1979

Time dependence of maximum flow as an index of nonuniform emptying.

Nonhomogeneous lungs are predicted to exhibit time dependence of maximal expiratory flow (Vmax): faster regions would contribute more flow early in the expiration, whatever the initial volume, resulting in different Vmax at a given total lung volume, depending on how long flow limitation has been operating. To test this concept a new technique was developed that permits accurate superimposition of Vmax data over small volume intervals. When quick-release interrupted partial curves with similar volume history but different volume of initiation were compared over their late common-volume segments, the volume-history effects could be differentiated from time dependence of the Vmax. Such time dependence was found in 7 of 7 bronchitics, 3 of 5 smokers, and 0 of 14 nonsmokers tested. We conclude that the emptying during the forced expirations is not uniform even in mild disease states and the time dependence of Vmax is a sensitive test of lung inhomogeneity.

Adult↗
PubMedDate not supplied

Coated vesicles from the protozoan parasite Trypanosoma brucei: purification and characterization.

A procedure was developed to purify a coated vesicle fraction from the protozoan parasite Trypanosoma brucei. Electron microscopy revealed a difference between T. brucei coated vesicles and clathrin-coated vesicles from other eukaryotes: trypanosome vesicles were larger (100 to 150 nm in diameter) and contained an inner coat of electron-dense material in addition to the external coat. Evidence suggests that the internal coat is the parasite's variant surface glycoprotein (VSG) coat. The SDS-PAGE analysis shows the major protein of T. brucei coated vesicles has a molecular mass of 61 kD, similar to VSG; this protein was recognized in an immunoblot by anti-VSG serum. Trypanosome coated vesicles also contain a protein which comigrates with the major protein (clathrin) of coated vesicles purified from rat brains. However, this protein is a minor component and it is not serologically cross-reactive with mammalian clathrin. Immunoblot analysis demonstrated that the parasite vesicles contained host IgG, IgM, and serum albumin.

Animals↗
PubMedDate not supplied

Effect of high dose inhaled acetic acid on airway responsiveness in Fischer rats.

BACKGROUND: Sudden, severe airway injury has been associated with an acute, and at times persisting, airway hyper-responsiveness with clinical features of asthma, termed reactive airways dysfunction syndrome (RADS). An attempt was made to develop a rat model of RADS by exposing inbred Fischer rats to inhaled 8 N acetic acid for 2 mins (13 N inhalation was lethal). METHODS: Lung resistance (RL) and lung elastance (EL) were measured in 14 eight- to 10-week old male rats. Baseline responsiveness to methacholine was quantified by calculating the dose required for doubling of RL. The next day, the study group (n=11) was exposed to aerosolized acetic acid. Control animals (n=3) were similarly exposed to buffered saline solution. RESULTS: Acetic acid exposure resulted in a significant (P<0.02) increase in RL (by 80%) and EL (by 67%), lasting less than 10 mins postexposure, but no significant change in methacholine responsiveness at one day and seven days postexposure. CONCLUSIONS: Failure to induce persistent airway hyper-responsiveness may relate to the choice of animal, choice of irritant, or insufficient level or duration of exposure, or may reflect a lack of individual predisposing cofactors such as smoking or underlying asthmatic predisposition.

Acetic Acid↗
PubMedDate not supplied

Red cell distribution width in sickle cell disease.

Red cell distribution width (RDW), an electronically determined index of anisocytosis, was examined in 60 patients with sickle cell anemia (Hb SS), 28 patients with hemoglobin sickle cell (SC) disease, and seven patients with sickle cell-beta(+) thalassemia (S-thal). All patients were adults and in the steady state of their disease. The RDW was greater in sickle cell patients than in 39 healthy, age and race matched controls without hemoglobinopathy (Hb AA). Patients with sickle cell anemia had higher mean RDW than those with Hb SC disease or with S-thal. The mean RDWs in the latter two disorders were not significantly different. In SS patients, the RDW correlated significantly with the degree of anemia and reticulocytosis. A group of 18 SS patients was studied while in acute painful crisis. Their mean RDW was not different from that in the steady state. Mean WBC and red cell volume, however, were significantly higher during pain crisis.

Adult↗